1. Field of the Invention
This invention relates to the field of chemical analysis and more specifically to the field of sample gas collection and analysis.
2. Background of the Invention
Chemical analysis often includes analyzing the amount of carbon or other elements such as nitrogen in a sample. Conventional practice for detecting carbon or such other elements in samples (i.e., solid, sludge or aqueous samples) employs techniques to convert the element of interest to a gas product prior to making the measurement. For instance, through oxidation or combustion, carbon in the sample may be combined with oxygen to produce carbon dioxide. The gas of interest is typically transferred to a calibrated analyzer (i.e., total organic carbon analyzer) by which the gas of interest is measured in a single-pass measurement to determine the level of product present in the sample. Drawbacks include the inability to store a sample for later analysis. Additional drawbacks with the single-pass measurement include the inability to satisfy a need for multiple analyses of a sample. Further drawbacks to the single-pass measurement include no opportunity to re-test after adjusting system parameters when calibration ranges are exceeded or detection limits are not achieved.
Conventional analyzers use a variety of oxidation techniques including combustion chemical reactions and catalytic reactions to convert target products to the analytical gas for measurement by the analyzer detection system. For instance, an example of a conventional analyzer detector is a nondispersive infrared sensor (NDIR). Drawbacks to current analyzer designs include the limitation of the detector range capability. In addition, direct measurement systems drive operational inefficiencies involving samples with a high concentration of the product of interest and generate gas concentrations above the calibration or saturation points of the detector. Additional inefficiencies include samples with concentrations of the product of interest that are too low to generate gases or with concentrations above the detection limit of the detector.
Consequently, there is a need for an improved process for measuring the level of a component in a sample. Further needs include an improved process that allows for multiple measurements to be made on the gases generated from a single sample. Needs also include an improved process that provides analyzer designs to operate over a broader dynamic range and be fault tolerant to over and under ranging.